Argonauta nodosa, also known as the knobby or knobbed argonaut, is a species of pelagicoctopus. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell (hence the name paper nautilus). The shell is usually approximately 150 mm in length, although it can exceed 250 mm in exceptional specimens; the world record size is 292.0 mm.[3]A. nodosa produces a very characteristic shell, which is covered in many small nodules on the ridges across the shell, hence the specific epithetnodosa and common name. These nodules are less obvious or even absent in juvenile females, especially those under 5 cm in length.[4] All other argonaut species have smooth ridges across the shell walls.[4]

Eggcases of A. tuberculata and A. gracilis from Thomas William Kirk's description of the latter.[2] Both taxa are now considered synonyms of A. nodosa.[5]

Females grow to 100 mm ML and 300 mm total length, while males do not exceed 40 mm in length.[4] The specialised webbed arm pair of this species is covered in numerous chromatophores. Mark Norman notes that "the colour of these webs can quickly change from maroon red to reflective silver".[4]

It has been reported that the egg clusters of A. nodosa from southern Australia can be clearly divided into three portions, each with eggs at a similar developmental stage.[9] Similar development has been observed in the egg masses of Argonauta bottgeri.[10]

A. nodosa is occasionally involved in mass strandings along the South African and southern Australian coastlines. The strandings are seasonal and generally occur between April and August, towards the end of the animals' spawning season.

^Nesis, K. N. (1977). "The biology of paper nautiluses, Argonauta boettgeri and A. hians (Cephalopoda, Octopoda), in the western Pacific and the seas of the East Indian Archipelago". Zool. Zh. 56: 1004–1014.